Recovery of soluble salts from natural brines or the like



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This, invention relates, primarily, to the recovery of soluble salts from natural biines wortthe like, and involves a unique process 4 therefor.

The essential object is to efiect recovery of potassium salts, borax and sodium carbonate from a mixture of these salts, and others,

and from each other.

Another object is more specifically to rei cover potassium salts, borax and sodium carbonate vfrom mixtures of sodium chloride, ,sodiurn sulfate, sodium carbonate, a potassi'um salt, and borax in solid state, such as can be obtained from evaporationof the natural brines occurring at Scarles Lake,

located in San Bernardino County, State or California, and elsewhere. The Searles Lake brine has a content substantially as follows:

' Per cent.

Borax (anhydrous) 1. 60 Sodium carbonate 4.70 Sodium chloride 16.50 Sodium sulfate 6. 90 Water .65. 65

More or less broadly expressed, the process comprises leaching the mixture of solid salts with a hot solution which contains sodium chloride, sodium sulfate, sodium borate and a potassium salt, these salts not being in solution equilibrium with each other when the solution is either hot or cold, therebeing a.

suficient amount of calcium oxide, or its equivalent to convert all, or a substantial f portion, of

meta-borate, v

It is, of course, contemplated that the addition of a caustic soda to the solution'will accomplish the same result. luse calcium oxide or calcium hydroxid, however, because is more convenient and less expensive.

The relative amounts of the named salts present in the solution will automatically adanereupon separated from the deposited the sodium tetra-borate to sodium wisest ru s m a, 1927; serial-no. 1ss,e09.

salts, and is theh subjected to the action of v carbondioxid, whereby all of the contained sodium carbonate is converted to sodium'bicarbonate which, being nearly insolublein the solut on, is mostly deposited therefrom. The solution is then separated from the deposited sodium bicarbonate. This last solutionis of the charatcer which I use to leach the mixed solid salts above referred to.- j i In practice, this last-mentioned solution is heated and then brought in contact with the mixed solid salts to be leached, together.

with a sufiicient amount of calcium oxide,

or its equivalent, to convert all, or a sufli'cient amount, of the contained sodium tetra-borate into sodium meta-boratewhich is much more soluble than sodium tetra-borate-so that, when the solution is cooled, none of the contained borate can deposit therefrom. The 5 particular object of this step is to insure nonseparation of the borate from the solution durin the cooling thereof, after leaching of the so id mixed salts.

The hot solution, in contact with the mixed solid salts, dissolves therefrom the, potasmum salt and borax, for these last-named salts are much more soluble in the hot soluthii than they were When the solutionwas co Owing to its previous treatment with carbon. dioxid, and the subsequent contact with calcium oxid, the leaching solution contains no sodium carbonate and,'consequent1y, dissolves sodium carbonate from the solid mixed salts. w v

In the case of mixed salts of the aforementioned relative composition contained in salts from Searles Lake brine, if the amount used of the mixed salts and the leaching solution are so proportioned that a minimum portion of the solution will just dissolve all of the potassium salt of the solid mixe salts, it usually will also dissolve all of the borax and all of the sodium carbonate oi? the mixed solid salts, leaving sodium chlorid and sodium sulfate, alone, undissolved.

lllhen the potassium salt, boraz: and sodium carbonate have dissolved from the solid mixed salts as completely as desired, the

hot solution is separated from the undissolved solid salts by appropriate means, such (for instance) as in a centrifuge, and the solution is cooled to any desired tempera ture, whereby the potassium salt alone deposits therefrom.

dium bicarbonate.

lution to the action of carbon dioxid The cooled solution is separated from the deposited potassium salt, and the latter is lightly washed to remove any adhering mother liquor and it is, then, in substantially pure condition, usuallyrequiring no further refining.

The cooled solution is then subjected to the action of carbon dioxid until the contained sodium meta-borate is converted to sodium tetra-borate. Sodium tetra-borate, being. much less soluble than was, the so dium meta-borate, crystallizes from the solution as borax. The solution is separated from the deposited borax by appropriate means, such as in a centrifuge, and the borax is lightly 'washed to remove any adhering mother liquor and is, then, in substantially pure condition Without further refining.

The solution is next subjected to the action of carbon dioxide'until all of the contained sodium carbonate is converted to so- The latter is very little soluble in the solution, and mostly separates therefrom. The deposited sodium bicarbonate is separated from the solution by appropriate'means, such (for instance) as in a centrifuge, and is lightly washed to remove any adhering mother liquor and is, then, in substantially pure condition, ready to be sold as bicarbonate of soda, or to be reduced to so a ash by calcination.

The mother liquor from the sodium'bicarbonate is then" used to dissolve more potassium salt, borax and sodium carbonate from more solid mixed salts, with more calcium oxide or its equivalent, thus completing the cycle and providing a means whereby the same solution may -be used over and over, indefinitely.

What I claim is:

1. The method of'recovering a potassium salt, borax and sodium carbonate from a mixture of a potassium salt, borax, sodium carbonate, sodium sulfate and sodium chlorid, including the steps of converting a portion of the borax to sodium meta-borate, leaching the solid mixed salts with a hot solution containing a potassium salt, a sodium borate, sodium sulfate and sodium chlorid, separating the hot solution from the undissolved solid salts, cooling the solution, separating the deposited potassium salt from the cooled solution, subjecting the cooled soseparating the deposited borax from the solution, subjecting this solution to the action of carbondioxid, separating the deposited sodium bicarbonate from the solution, and usin this final solution as'the initial solution W1erewith to dissolve the potassium salt, sodium borate and sodium carbonate from more of the mixed solid salts to repeat the cycle;

2. The method of recovering a'potassium salt, borax and sodium carbonate from a mixture of a potassium salt, borax, sodium carbonate. sodium chlorid and sodium sulfate in solid state, which includes dissolving the potassium salt, borax'and sodium carbonate from the solid mixed salts by means of a hot solutionrcontainingsodium chlo- ;r1d,'sod1um sulfate, sodlum borate and a cooled solution to the action of carbon dioxid until the contained borate is converted to sodium tetra-borate, separating the dcposited borax from thesolution, subjectim the solution to the action of carbon dioxid until the contained'sodium carbonate is converted to sodium bicarbonate, separating the deposited sodium bicarbonate from the solution, and using the solution to dissolve more potassium salt, borax and sodium carbonate from more mixed solid salts to repeat the cycle.

3. The method of recovering a potassium salt, borax and sodium carbonate from mixtures thereof, with sodium chlorid and sodium sulfate in solid state, which includes leaching the mixed solid salts in the presence of calcium oxide with a hot solution containing potassium, a sodium borate, sodium chlorid and sodium sulfate, separating the hot solution from the undissolved portion of the solid salts, cooling the solution, separating the deposited potassium salt from the cooled solution, subjecting the cooled solution to the actionof carbon dioxid until substantially all borates therein are converted to sodium tetra-borate, separating the deposited borax from the solution, subjecting the solution tothe action of carbon dioxid until the sodium carbonate contained therein is converted to sodium bicarbonate, separating the deposited sodium bicarbonate from the solution, and using this solution, reheated and in the presence of calcium oxide, to dissolve more potassium salt, borax and sodium carbonate from more mixed solid salts to repeat the cycle.

4. Themethod of recovering a potassium salt, borax and sodium carbonate from mixtures thereof, with sodium chlorid and so dium sulfate in solid state, which includes 'the step of leaching the mixed solid salts in the presence of calcium oxide with a hot solution containing potassium, a sodium borate, sodium chlorid and sodium sulfate.

5. The method of recovering a potassium salt, borax and sodium carbonate from mixtures thereof, with sodium chlorid and sodium sulfate in solid state, which includes the steps of leaching the mixed solid salts in the presence of calcium oxide with a hot solution con'tainin potassium, a sodium borate sodium ch orid and sodium sulfate, cooling the solution, and subjecting it suclfll) tures thereof, with sodium chlorid and sodium sulfate in solid state. which includes the steps of "leaching the mixed solid salts in the presence of calcium oxide with a hot solution containing potassium, a sodium b0- 10 rate, sodium chlorid and sodium sulfate, cooling the solution and subjecting it successively to the action of carbon dioxid and eflecting separation of the borates and sodium carbonate, and re-using the resultant '15 solution in a succeeding recovery-cycle.

In testimony whereof I affix my signature. CLINTON E. DOLBEAR. 

